Abilities

Effect Spore - Has a 10% chance of causing Sleep. It can also, however, cause Poisoning or Paralysis.

Other

Disobedient Pokémon will fall asleep sometimes.

Cures, Immunity, and Prevention

Items

Awakening

Full Heal

Full Restore

Old Gateau

Sacred Ash

Casteliacone

Heal Powder

Chesto Berry

Lum Berry

SLPCureBerry

Blue Flute

PokéFlute

Moves

Heal Bell

Aromatherapy

Safeguard

Wake-Up Slap

Uproar

Abilities

Vital Spirit

Insomnia

Leaf Guard

Natural Cure

Shed Skin

Healer

Hydration

Early Bird

Other

In Pokémon XD: Gale of Darkness, you can use the "Call" button to awake a sleeping Pokémon.

Console Series

Pokémon Stadium

Sleep lasts for 1 to 3 turns (Its randomly chosen). The Pokémon in question cannot make any moves during this duration of Sleep. Pokémon cannot make a move the turn they wake up.

Pokémon Stadium 2

Sleep is exactly the same as Pokémon Stadium, save for one change. A Pokémon can make a move the turn they wake up now.

Pokémon XD: Gale of Darkness

Sleep lasts for 1 to 5 turns (Its randomly chosen). The Pokémon in question cannot make any moves during this duration of Sleep.

Pokémon Battle Revolution

Sleep lasts for 1 to 5 turns (Its randomly chosen). The Pokémon in question cannot make any moves during this duration of Sleep.

Side Games

Pokémon Mystery Dungeon series

In the Mystery Dungeon series, there are many versions of Sleeping. The first is Asleep, where the Pokémon cannot act for 3 to 6 turns (Its randomly changes). The next is Napping, which is just like Asleep, but once you awaken, all other status effects are healed. The next is Nightmare, where you cannot attack for 4 to 7 turns, and once you awake, it takes 8 HP. The next is Yawning, where it causes Asleep in three turns. The final is Sleepless, which prevents any of the former from occurring.

Pokémon TCG series

Since both games follow the Trading Card Game rulings, the Pokémon can fall asleep. When Sleeping, it cannot attack or retreat. Every turn, the trainer must flip a coin. If Heads, the Pokémon wakes up. If Tails, the Pokémon remains asleep. When it is asleep, the card is turned counterclockwise.

Trading Card Game

In the Card Game, there are five status effects that mimic common ones from the games. When Sleeping, it cannot attack or retreat. Every turn, the trainer must flip a coin. If Heads, the Pokémon wakes up. If Tails, the Pokémon remains asleep. When it is asleep, the card is turned counterclockwise.

Anime

In the Anime, Pokémon and People often fall asleep, though not always with an effect. The following lists only times when they fall asleep through an attack.

In Pokémon! I Choose You!, a Gengar uses Hypnosis put the opponent's Nidorino to sleep, forcing the Nidorino's trainer to switch.

In Challenge of the Samurai, Ash's Butterfree used Sleep Powder to calm a swarm of Beedrill. He later tried to use Sleep Powder on Misty's Staryu in The Water Flowers of Cerulean City, but Staryu avoided its effects by diving underwater.

In Hypno's Naptime, the abuse of Hypno's Hypnosis had been causing the Pokémon of HopHopHop Town to fall asleep without warning. It put the town's children, as well as Misty under a trance, in which they would run away to a pond and start acting like Pokémon.

In The Ninja Poké-Showdown, Koga's Venomoth used Sleep Powder on Ash's Pidgeotto during their gym battle, forcing Ash to switch.

A Jigglypuff that followed Ash and his friends almost always used Sing whenever it appeared. When it discovered that its "audience" slept through it song, the balloon Pokémon doodled on the sleeping Pokémon, and people, before leaving in a huff. However, its songs have still helped out Ash and the people he has met from time to time. In its debut episode, its song helped the cranky people of Neon Town finally fall asleep, after which, they woke up much more agreeable and friendly. In the following episode, Jigglypuff's song was able to put back to sleep the angry ancient Pokémon that slept there.

In Friend and Foe Alike, Ritchie's Butterfree, Happy, used Sleep Powder on Ash's Squirtle during their league battle. Squirtle, already tired from a previous attack by Jessie, James, and Meowth, was declared unable to battle.

In The Rise of Darkrai, Darkrai used its Dark Void in order to warn the people of Alamos Town about the coming attack of Dialga and Palkia. Unfortunately, the Bad Dreams that it caused led Baron Alberto to see Darkrai as a threat.
In League Unleashed!, Nando's Kricketune used Sing to put Ash's Heracross to sleep. However, Heracross was able to counter it with Sleep Talk.

In The Semi-Final Frontier!, Tobias's Darkrai used a combination of Dark Void and Dream Eater against Ash's Heracross, quickly knocking it out. Darkrai also put Sceptile to sleep, but it managed to wake up just in time to take it out with Leaf Blade.

Manga

The Electric Tale of Pikachu

In Chapter 2: Play with me Misty, after Ash's Metapod evolves, it uses Sleep Powder to make Misty's Gyarados fall asleep.